1. Field of Invention
The invention relates to a switch device and, in particular, to a KVM switch for multiple chaining and with high compatibility and the method thereof.
2. Related Art
With the rapid development in information technology, computers and their peripherals become very popular. Computer users often use the mouse and keyboard to control the computers. Through the monitors or speakers, the computer users can monitor the state of the computers. Sometimes a user may have more than one computer to process different types of things. Traditionally, each computer is equipped with one set of input/output (IO) peripheral devices, including the keyboard, mouse, monitor, and speakers. However, this is a waste of money and space if one has several computers.
On the other hand, large system businesses or enterprise internal networks often involve tens to thousands servers. Each server needs a monitor, a keyboard and a mouse to for management. In practice, one rarely needs to manipulate these devices. Most of the time, the servers do not need to be controlled by the manager. In this situation, it is totally unnecessary, costly, and wasting the space to have a set of IO peripheral devices for each server.
Therefore, a keyboard video mouse (KVM) switch is proposed to use at least one set of operation device to manage several computers. Using the KVM switch does not only solve the cost problem, it simultaneously solves the problems of equipment and space. It may also conquer the compatibility problem among different interfaces.
However, due to the hardware design and cost restriction of an individual KVM switch, the number of manipulating devices and computers it can accommodate is limited. On the other hand, it is not easy to connect conventional KVM switches together. When several manipulating devices simultaneously access multiple computers, the connection agreements among the manipulating devices and computers are often different. The commonly used connection agreements include the universal serial bus (USB) interface, the serial port (COM) interface, or the personal system/2 (PS/2) interface.
The different connection agreements will reduce the compatibility of the KVM switches and the signal exchange efficiency among them. For example, when the connection agreement of the keyboard is the USB interface while that of the computer is the PS/2 interface, the conventional KVM switch usually converts the electrical signal to/from the keyboard to be PS/2 compatible.
Nevertheless, such a method is not suitable for multiple chaining KVM switches. If they need to transmit electrical signals in different connection agreements, their circuits have to be able to understand various connection agreements. This does not only increase the design difficulty, the compatibility is still an issue that serious reduce its efficiency.
The above-mentioned drawbacks result in a lot of inconvenience in practical uses. For large system businesses or the internal networks of mid-size enterprises, in particular, if the KVM switches cannot simultaneously support a large number of manipulating devices and computers, they do not only increase the costs for constructing and maintaining the system but also reduce the communication efficiency of the whole network.